Lithium secondary battery

Abstract

Charge-discharge cycle performance is improved in a lithium secondary battery utilizing a material containing silicon as a positive electrode active material. A lithium secondary battery includes a negative electrode ( 2 ) containing silicon as a negative electrode active material, a positive electrode ( 1 ) containing a lithium-transition metal composite oxide, and a non-aqueous electrolyte. Lithium carbonate is added in the positive electrode ( 1 ), and carbon dioxide is dissolved in the non-aqueous electrolyte.

1 . A lithium secondary battery comprising: 
 a negative electrode containing silicon as a negative electrode active material;    a positive electrode containing a lithium-transition metal composite oxide as a positive electrode active material; and    a non-aqueous electrolyte, wherein    lithium carbonate is contained in the positive electrode, and carbon dioxide is dissolved in the non-aqueous electrolyte.    
     
     
         2 . The lithium secondary battery according to  claim 1 , wherein the lithium carbonate in the positive electrode is uniformly mixed with the lithium-transition metal composite oxide.  
     
     
         3 . The lithium secondary battery according to  claim 1 , wherein the amount of the lithium carbonate contained in the positive electrode is within the range of from 0.3 weight % to 5 weight % with respect to the lithium-transition metal composite oxide.  
     
     
         4 . The lithium secondary battery according to  claim 2 , wherein the amount of the lithium carbonate contained in the positive electrode is within the range of from 0.3 weight % to 5 weight % with respect to the lithium-transition metal composite oxide.  
     
     
         5 . The lithium secondary battery according to  claim 1 , wherein lithium carbonate is contained in the lithium-transition metal composite oxide and the total amount of the lithium carbonate contained in the lithium-transition metal composite oxide and the lithium carbonate separately contained in the positive electrode is within the range of from 0.3 weight % to 5 weight % with respect to the lithium-transition metal composite oxide.  
     
     
         6 . The lithium secondary battery according to  claim 2 , wherein lithium carbonate is contained in the lithium-transition metal composite oxide and the total amount of the lithium carbonate contained in the lithium-transition metal composite oxide and the lithium carbonate separately contained in the positive electrode is within the range of from 0.3 weight % to 5 weight % with respect to the lithium-transition metal composite oxide.  
     
     
         7 . The lithium secondary battery according to  claim 5 , wherein the lithium carbonate contained in the lithium-transition metal composite oxide exists in and near a surface of the lithium-transition metal composite oxide.  
     
     
         8 . The lithium secondary battery according to  claim 6 , wherein the lithium carbonate contained in the lithium-transition metal composite oxide exists in and near a surface of the lithium-transition metal composite oxide.  
     
     
         9 . The lithium secondary battery according to  claim 1 , wherein the positive electrode comprises a positive electrode current collector made of a conductive metal foil, and a mixture layer arranged on the positive electrode current collector and containing the positive electrode active material, the lithium carbonate, a positive electrode binder, and a positive electrode conductive agent.  
     
     
         10 . The lithium secondary battery according to  claim 2 , wherein the positive electrode comprises a positive electrode current collector made of a conductive metal foil, and a mixture layer arranged on the positive electrode current collector and containing the positive electrode active material, the lithium carbonate, a positive electrode binder, and a positive electrode conductive agent.  
     
     
         11 . The lithium secondary battery according to  claim 1 , wherein the negative electrode comprises a negative electrode current collector made of a conductive metal foil, and a mixture layer arranged on the negative electrode current collector and containing a binder and active material particles containing silicon and/or a silicon alloy.  
     
     
         12 . The lithium secondary battery according to  claim 2 , wherein the negative electrode comprises a negative electrode current collector made of a conductive metal foil, and a mixture layer arranged on the negative electrode current collector and containing a binder and active material particles containing silicon and/or a silicon alloy.  
     
     
         13 . The lithium secondary battery according to  claim 11 , wherein in the negative electrode, the mixture layer is sintered on a surface of the negative electrode current collector.  
     
     
         14 . The lithium secondary battery according to  claim 12 , wherein in the negative electrode, the mixture layer is sintered on a surface of the negative electrode current collector.  
     
     
         15 . The lithium secondary battery according to  claim 1 , wherein the amount of the carbon dioxide dissolved in the non-aqueous electrolyte is 0.01 weight % or greater.  
     
     
         16 . The lithium secondary battery according to  claim 2 , wherein the amount of the carbon dioxide dissolved in the non-aqueous electrolyte is 0.01 weight % or greater.  
     
     
         17 . The lithium secondary battery according to  claim 3 , wherein the amount of the carbon dioxide dissolved in the non-aqueous electrolyte is 0.01 weight % or greater.  
     
     
         18 . The lithium secondary battery according to  claim 4 , wherein the amount of the carbon dioxide dissolved in the non-aqueous electrolyte is 0.01 weight % or greater.